A middle school student opened fire in his gym with a shotgun today and critically wounded two students in Roswell, N.M., according to authorities.

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The injured were a 13-year-old girl and a 12-year-old boy who were "simply sitting in their gym waiting to go to class," New Mexico Gov. Susana Martinez said. The shooting occurred shortly before class was to begin at Berrendo Middle School.

The Eastern New Mexico Medical Center confirmed it treated two patients, who were then air lifted to the University Medical Center in Lubbock, Texas, located about 175 miles from the middle school.

A spokesperson for UMC said the boy, who the governor said was 12, is out of surgery and is listed in critical condition. The girl, 13, is also being treated at the hospital and is listed in serious condition, according to the spokesperson. A school staff member suffered a minor injury and declined treatment.

Odiee Carranza, an eighth grade student, told the Associated Press a boy bumped into her as he rushed toward the gym and apologized to her. When the boy entered the gym, Carranza said she saw him pull a gun out of a band instrument case and begin shooting.

She said he shot another boy twice in the face and shoot a girl in the arm.

"Then he shot up in the sky, then dropped the gun, and then some teacher grabbed the kid that had the gun," Carranza told the AP.

Authorities said the weapon was a shotgun and the shooter was a 12-year-old seventh grader.

The governor said a school staffer and an off-duty New Mexico State Police lieutenant who was dropping his child off at the school were instrumental in helping to end the active shooter situation before more people were injured.

New Mexico State Police Chief Pete Kassetas said by the time his deputies arrived around 8: 11 a.m., "the weapon, which we believe is a shot gun, was laid on the ground."

The alleged shooter was taken into custody and the chief said it is believed he acted alone.

Kassetas did not disclose a possible motive, but said investigators are "looking at social media outlets and the different forms of communication these kids use to talk to each other."

After the scene was secure this morning, students were bused from the school to Roswell Mall where police said parents will be allowed to pick up their children. Authorities asked parents to stay away from the school during the investigation.

The Roswell incident is the latest school shooting to rattle the country. It comes one month after a gunman open fire at Arapahoe High School in Colorado.

Police said Karl Pierson, 18, who was armed with a shotgun, machete and had Molotov cocktails in his backpack, was intent on seeking "revenge" on the school's debate team instructor who had dropped him from the team.

Pierson came upon senior Claire Davis, 17, while looking for his intended target. He critically wounded the high school senior before police said he took his own life.

Davis died on Dec. 21 from her injuries.

The Arapahoe shooting took place on the eve of the first anniversary of the Sandy Hook school shooting in Newtown, Conn., in which 27 people - most of them first graders - were killed.

The Arapahoe shooting also took place on the eve of the first anniversary of the Sandy Hook school shooting in Newtown, Conn., in which 27 people - most of them first graders - were killed.